Electrically heated surgical cutting instrument

ABSTRACT

A surgical cutting instrument includes an electrically heated cutting edge and an automatic control system for maintaining the cutting edge at a constant high temperature for sterilizing the blade, cutting tissue, and cauterizing the incised tissue to reduce hemorrhage from the cut surfaces of the tissues (hemostasis).

United States Patent [151 Cage et al.

[ 1 3,826,263 [451 July 30, 1974 1 ELECTRICALLY HEATED SURGICAL CUTTINGINSTRUMENT [75] Inventors: John M. Cage, Los Altos; Robert F. Shaw, SanFrancisco; Paul E. Stoft, Menlo Park, all of Calif.

[73] Assignee: Robert F. Shaw, Palo Alto, Calif. 22 Filed: Aug. 7, 1972i [63] Related US. Application Data Division of Application Ser. No.63,645, Aug. 13, 1970.

] US. Cl l28/303.l, l28/303.l4, 128/303.l7 Int. Cl. A6lb 17/38, A6ln3/00 1 Field of Search 30/140; 219/499;

[56] References Cited UNITED STATES PATENTS 3/1887 Goodwillie 128/303.14X 11/1929 Groff 128/303.14 2/1931 Hyams l28/303.l4

T0 FIRST CONTROL srsrrn T0 SECOND CONTROL SYSTEM 1,930,214 10/1933Wapplel 128/303.14 2,012,937 9/1935 Beuoy 128/303.14 X 2,012,938 9/1935Beuoy 128/303.l4 X 2,120,598 6/1938 Beuoy 128/303.14 X 2,795,697 6/1957Nagel 219/499 X 3,526,750 9/1970 Siegcl 30/140 X PrimaryExaminer-Richard C. Pinkham Assistant Examiner-Richard J. ApleyAttorney, Agent, or FirmA. C. Smith 57] ABSTRACT A surgical cuttinginstrument includes an electrically heated cutting edge and an automaticcontrol system for maintaining the cutting edge at a constant hightemperature for sterilizing the blade, cutting tissue, and cauterizingthe incised tissue to reduce hemorrhage from the cut surfaces of thetissues (hemostasis).

3 Claims, 3 Drawing Figures This is a divisional application of pendingapplication Ser. No. 63,645, filed Aug. I3, 1970.-

BACKGROUND OF THE INVENTION The control of bleeding during surgeryaccounts for a major portion of the total time involved in an operation.The bleeding that occurs when tissue is incised obscures the surgeonsvision, reduces his precision and often dictates slow and elaborateprocedures in surgical operations. :Each bleeding vessel must be graspedin pincer-like clamps to stop the flow of blood and the tissue andvesselwithin each clamp must then be tied with pieces of fine thread.These ligated masses of tissue die and decompose and thus tend to retardhealing and promote infection.

SUMMARY OF THE INVENTION Accordingly, the present invention provides asurgical cutting instrument having a cutting edge which is electricallyheated to a constant high temperature for sterilizing the blade, cuttingthe tissue and cauterizing the surfaces of the incision, therebyallowing surgery to be more rapidly performed. This is accomplished inaccordance with the illustrated embodiment of this invention byproviding an electrically heated element disposed as the cutting edgesof the blade and by providing a control system which maintains thecutting edge at a high substantially constant temperature during itsuse. The hot cutting edge according to the present invention decreasesthe amount of tissue that is damaged and reduces the tendency of theinstrument to stick to the heated tissue in the incision. The materialused in the electrically heated cutting edge hasa negative temperaturecoefficient of resistance to insure that electrical power applied to thecutting edge is dissipated primarily in the regions thereof which tendto be cooled by contact with tissue. The temperature at which thecutting edge of the blade is maintained depends upon such factors as thenature of thetissue to be cut, the speed of cutting desired, the degreeof tissue coagulation desired, and the non-adherence of the blade totheincised tissue and generally is maintained between 300-l ,000 C. fortypical incisions. The instantaneous temperature of the cutting edge ismonitored by measuring the resistance of the heating element itself orthrough the use of thermocouple elements disposed in the blade near thecutting edge, and the monitoring signal thus derived controls the powerapplied to the heating element. The handle of the cutting instrument isthermally insulated from the blade to permit comfortable use of theinstrument and the handle and blade with its electrically heated cuttingedge are detachable for easy replacement and interchangeability .withblade,

. scoops and cutting edges of various shapes and sizes determined by thenature of the incision to be made and the tissue to be cut.

DESCRIPTION OF THE DRAWING FIG. 1 is a schematic diagram showing thecutting instrument and the temperature control system therefor,according to the preferred embodiment of the present invention, andFIGS. 2 and 3 are pictorial views of other embodiments of cuttinginstruments according to the present invention for use with circuitry asshown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1 of thedrawing, there is shown the surgical cutting instrument 9 connected to atemperature-measuring and power-controlling system 11. The cuttinginstrument 9 includes a thin ceramic card 12 in the desired shape of asurgical cutting blade which is detachable from the handle or holder 10.An electrically heated element 13 is disposed along the leading edge ofthe card 12 to form its cutting edge and is electrically connected tothe control circuit through the cable 14 and the connectors 16. Theelement 13 may be a single filament attached to the edge of the card 12,for example, using conventional ceramic welding materials or may be alayer of electrically conductive material vapor-deposited along the edgeof the card 12. Also, the heating element 13 may have sufficientcross-sectional area to be self-supporting, as shown in FIG. 2, so thatthe blade 18 is formed entirely by the element 13 alone. The materialused in the element 13 ideally should have a negative temperaturecoefficient of resistance so that as selected portions of the elementcool when in contact with tissue, the resistance of such portions willincrease and thereby localize the portions of the element 13 in whichadditional power supplied bythe control system will be dissipated. Thetemperature of the element may thus be maintained substantially constantover the entire length thereof as portions of the element 13 contacttissue. Suitable materials having negative temperature coefficients ofresistance include silicon carbide, carbon, boron silicate and suchsemiconductor materials as silicon and germanium. Of course, materialhaving a positive coefficient of resistance may also be used. However,when materials of this type are used, care should be taken to shape theelement 13 so that substantially the entire length of the element 13contacts tissue in use. This is required to prevent the additional powersupplied by the control system 11 from being dissipated in the portionsof the element which do not cool when in contact with tissue and, hence,which have higher resistance than the cooler portions. For cuttingapplications where it is not convenient to shape the element 13 so thatits entire length is in contact with tissue each time it is used, theelement 13 may consist of a plurality of electrically isolated elements13 and 13, as shown in FIG. 3, with each of the elements 13 and 13'connected to a separate temperature measuring and powercontrollingsystem of the type shown in FIG. 1.

The resistance of the element 13 is included in a bridge circuit 15which is connected to receive alternating signal appearing on lines 17and 19. The level of alternating signal appearing on lines 17 and 19and, hence, the power applied to element 13 is determined by theconduction angles of the controlled rectifiers 21 and 23 which areconnected in conduction opposition in parallel across the seriesresistor 25. Power is supplied to the control system 11 through theprimary and secondary windings 26 and 27 of power input transformer 29.Alternating line signal 28 applied to the transformer 29 is stepped downtypically to about 24 volts for the safety of the patient and thesurgeon and the average current flow per half cycle of the alternatingsignal-is determined in part by the series resistor 25 and by theconduction angle of a silicon-controlled rectifier 21, 23.

The operating temperature of the element 13 may be determined byadjusting one of the resistors, say resistor 31, in the bridge circuit15. Any variation in the operating temperature of element 13 from a setvalue unbalances the bridge 15 and produces a control signal 33 acrossthe diagonal terminals 35, 37 of the bridge circuit 15 which is eitherin phase or out of phase with the applied line signal, depending uponwhether the operating temperature of theelement is above or below theset value of operating temperature. A phase-shifting network 39 isconnected to the output terminals of the bridge circuit 15 for applyingthe error signal 44 with respect to ground to the input of erroramplifier 41 with a small amount of phase shift relative to the appliedline signal 28. This provides control of the conduction angle of thecontrolled rectifiers 21, 23 over a greater portion of a half cycle ofthe applied line signal. The output of amplifier 41 is applied to thethreshold detectors 43, 45 which respond to the amplified error signalattaining selected values slightly above and below zero. The thresholddetectors 47 and 49 thus activate the trigger pulse generators 47 and49'at the proper times in alternate half cycles of applied line signal28 to apply conduction-initiating pulses to the gate electrodes 51, 53of the controlled rectifiers 21, 23. Thus, increased conduction angle ofthe controlled rectifiers 21 and 23 increases the power applied to theelement 13 to maintain the element at a preselected operatingtemperature as the element tends to cool down in contact with skintissue. However, if the operating temperature of the element 13 shouldexceed the set value due, for example, to thermal overshoot upon removalof the element 13 from contact with skin tissue, the phase of the'errorsignal 33 with respect to the applied line signal reverses. This causesthe trigger pulse generators to supply conduction-initiating pulses tothe gate electrodes of the controlled rectifiers 21, 23 during alternatehalf cycles when these rectifiers are back biased. This causes adecrease in the power delivered to the element 13 with a concomitantdrop in its operating temperature to about the set value of operatingtemperature. When this occurs, the proper phase relationship betweenerror signal and line signal is restored and power is again supplied tothe element 13. Conversion of the control system 11 for operation withelements 13 having negative or positive temperature coefficients ofresistance merely requires that the trigger pulses from the generators47 and 49 be applied through reversing switch S to the proper controlledrectifier 21, 23 during the forward-biasing half cycle of line signal28.

It should be apparent that other temperature control systems may also beused to maintain the operating temperature of the element 13substantially constant at a preselected value. For example, athermocouple sensor may be disposed on the card 12 in close proximitywith the element 13 or a thermocouple element may even be formed onelement 13 using another material or dissimilar work function to formthe thermocouple junction. The signal from such thermocouple may then beused to control the operating temperature of the element 13 bycontrolling the power supplied thereto.

We claim:

l. A surgical instrument for cutting tissue with simultaneoushemostasis, the instrument comprising:

a blade-shaped support wafer of electrically insulating material havingdisposed thereon an electrically heatable element of electricallyconductive material having a resistance which varies as a function ofthe temperature thereof, the element including a plurality of sectionswhich form segments or portions of a tissue-cutting edge of said supportwafer, each of said sections conducting electrical current along saidedge for directly heating the edge; and

connection means providing electrical connections to each of saidsections for independently supplying electrical power thereto formaintaining the resistance of each of said sections at a substantiallyconstant selected value.

2. A surgical instrument as in claim 1 comprising:

means for each of said sections operatively coupled thereto for sensingthe electrical resistance of the corresponding section;

circuit means for each of said sections having an input for receivingelectrical current from a source and being responsive to the electricalresistance of the corresponding section of said element for altering theelectrical power supplied through said connection means to thecorresponding section from the signal received at said input to maintainthe temperature of the corresponding section substantially at apreselected value independent of the temperature of another section ofsaid element.

3. A surgical instrument as in claim 2 wherein each of said circuitmeans comprises a plurality of circuit elements and said correspondingsection connected in a bridge circuit having first and second pairs ofbridge terminals, and including control means coupling said input to thefirst pair of bridge terminals, and bridgebalance sensing meansconnected to the second pair of bridge terminals and to said controlmeans for altering the electrical power applied through the bridgecircuit to said corresponding section for maintaining the resistancethereof substantially at a preselected value.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,826,263 Dated July 30, 1974 Inventor (s) John M. Cage, Robert F. Shaw,and Paul E. Stoft It is certified that error appears in theabove-identified patent and that said Letters Patent'are herebycorrected as shown below:

In the title page, left column, at item [63] after "Aug. 13, 1970"delete and insert now abandoned,

which is a continuation of application Ser. No. 681,737, filed November9, 1967,- now abandoned.

Column 1, line 5, after "Aug. 13, 1970" delete and insert now abandoned,which is a continuation of application Ser. No. 681,737, filed November9, 1967, now

abandoned.

Signed and Eealcdthis eleventh Of November 1975 sen A nest:

RUTH C. MASON (nmml'ssiuncr nflurenls and Trademarks UNITED STATESPATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,826,263 Dated July30, 1974 Inventor (s) John M, Cage, Robert Shaw, and Paul E. Stoft It iscertified that error appears in the above-identified patent and thatsaid Letters Patent-are hereby corrected as shown below:

In the title page, left column, at item [63] after "Aug. 13, 1970"delete and insert now abandoned, which is a continuation of applicationSer. No. 681,737,

filed November 9, 1967, now abandoned.

Column 1, line 5, after "Aug. 13, 1970" delete and insert now abandoned,which is a continuation of application Ser. No. 681,737, filed November9, 1967, now

abandoned,

Signed and Sealed-this eleventh OF N0vember1975 [SEAL] A lies I:

1. A surgical instrument for cutting tissue with simultaneoushemostasis, the instrument comprising: a blade-shaped support wafer ofelectrically insulating material having disposed thereon an electricallyheatable element of electrically conductive material having a resistancewhich varies as a function of the temperature thereof, the elementincluding a plurality of sections which form segments or portions of atissue-cutting edge of said support wafer, each of said sectionsconducting electrical current along said edge for directly heating theedge; and connection means providing electrical connections to each ofsaid sections for independently supplying electrical power thereto formaintaining the resistance of each of said sections at a substantiallyconstant selected value.
 2. A surgical instrument as in claim 1comprising: means for each of said sections operatively coupled theretofor sensing the electrical resistance of the corresponding section;circuit means for each of said sections having an input for receivingelectrical current from a source and being responsive to the electricalresistance of the corresponding section of said element for altering theelectrical power supplied through said connection means to thecorresponding section from the signal received at said input to maintainthe temperature of the corresponding section substantially at apreselected value independent of the temperature of another section ofsaid element.
 3. A surgical instrument as in claim 2 wherein each ofsaid circuit means comprises a plurality of circuit elements and saidcorresponding section connected in a bridge circuit having first andsecond pairs of bridge terminals, and including control means couplingsaid input to the first pair of bridge terminals, and bridge-balancesensing means connected to the second pair of bridge terminals and tosaid control means for altering the electrical power applied through thebridge circuit to said corresponding section for maintaining theresistance thereof substantially at a preselected value.